The shooter, identified as James T. Hodgkinson, a 66-year-old home inspector from Illinois, was shot and killed by Capitol Police officers who were in Scalise's security detail.

Hodgkinson had several minor run-ins with the law in recent years and belonged to a Facebook group called "Terminate the Republican Party."

The FBI said it recovered a 9mm handgun and 7.62 caliber rifle from Hodgkinson. Authorities said the weapons were purchased legally. Hodgkinson had been living out of a van in the Alexandria area since March and officials said they found a camera, computer and cellphone inside the vehicle.

Scalise was rushed to MedStar Washington Hospital Center and was immediately taken into surgery. He remains in critical condition Thursday. At a press conference, President Trump says that wounded Scalise's condition is more difficult than people first realized. He says Scalise is "in some trouble."

On Thursday night, MedStar Washington Hospital Center issued a statement saying he was seen some improvement after undergoing another surgery.

"Earlier today, Congressman Steve Scalise underwent a second surgery related to his internal injuries and a broken bone in his leg," the hospital said. "He remains in critical condition, but has improved in the last 24 hours. The Congressman will require additional operations, and will be in the hospital for some time. At the request of the family, we will continue to provide periodic updates."

Also wounded was former congressional aide Matt Mika, who now works for Tyson Foods in its Washington office. Mika's family said the lobbyist was shot multiple times. He also remains in critical condition Thursday following surgery.

Zack Barth, an aide to Texas Rep. Roger Williams, was wounded but is expected to make full recovery.

U.S. Capitol Police Special Agent Crystal Griner is in stable condition after suffering gunshot wounds. She is still hospitalized. Fellow Special Agent David Bailey was not shot but was treated and released after suffering an injury during the incident. It was revealed on Thursday that two Alexandria Police officers had also engaged in gunfire with Hodgkinson.

Rep. Roger Williams (R-Texas) was injured after diving into the dugout during the incident.

Following the shooting, President Donald Trump urged Americans to come together as he assumed the role of national unifier for one of the first times in his presidency. On Wednesday night, Trump, accompanied by first lady Melania Trump, visited Scalise at the hospital. The pair brought a floral arrangement and visited with members of the House Majority Whip's family

The shooting raised questions about the security of members of Congress. While the top lawmakers, including Scalise, have security details, others do not and they regularly appear in public without protection.

The last time a lawmaker was shot was when Democratic Rep. Gabby Giffords of Arizona was hit in the head and grievously injured while meeting with constituents at a supermarket parking lot in 2011.